Crystal growth method of nitride semiconductor

ABSTRACT

The present invention relates to a method of manufacturing a nitride semiconductor, and, more particularly, a crystal growth method of a nitride semiconductor wherein a nitride semiconductor are grown on a nitride buffer layer including aluminums so that it is possible to improve electrical and crystalline characteristics.

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing anitride semiconductor, and, more particularly, a crystal growth methodof a nitride semiconductor wherein a nitride semiconductor are grown ona nitride buffer layer including aluminums so that it is possible toimprove electrical and crystalline characteristics.

BACKGROUND OF THE INVENTION

[0002] Photoelectric elements and electric elements using Group Ill-Vnitride semiconductors are developed actively. Luminescence diode and alaser diode with ultraviolet range or visible range are applied to manyfields and their application will be extended more widely in the nearfuture.

[0003] It is difficult to grow a nitride semiconductor film and elementsof a good quality since nitride substrate of a mono-crystal having agood character is hard to make.

[0004] So, conventionally, the nitrides were grown on double-substratesof such as GaAs, ZnO, Sapphire, SiC, etc. Among them, nitride filmsgrown on Sapphire substrate and SiC have specially a good quality enoughto be used widely for manufacturing elements.

[0005] SiC has a good electric conductivity but very expensive so thatmost elements are using the nitrides grown on substrate of Sapphire.

[0006] Improving the characters of the films of the nitridesemiconductors is due to the development of growth technology of thenitrides.

[0007] In order to grow a nitride film on upper substrate of Sapphire,the Sapphire substrate has to be treated at a high temperature, and thenbuffer layer is made on it at a low temperature (450˜600° C.). Afterthat, the nitride film is grown on the buffer layer at a hightemperature.

[0008] During this process, buffer layer growth is important.

[0009]FIG. 1 is shown a cross-sectional view of the stacking structureincluding the nitride semiconductors grown as a conventional method ofcrystal growth, which comprise the process of growing the buffer layerof the bivalent nitride on the upper substrate of sapphire and theprocess of growing the layers of the nitride semiconductor on saidgroup-2 nitride buffer layers.

[0010] The necessity of the buffer layer is due to the differencebetween thermal expansion and the lattice constant of a sapphiresubstrate and the nitride which grows on said sapphire substrate.Namely, to overcome the differences of said the thermal expansion andthe lattice constant between the nitrides and the sapphire substrate,the nitride semiconductor is grown after the layer of bivalent nitridewhich is selected in GaN, AlN, InN and SiNx or the compounds thereof, isgrown on a sapphire substrate, as shown FIG. 1.

[0011] The nitride film which was grown like the above is not singlecrystal but polymer or poly crystal so that it can be a seed layer to beable to grow a layer of the nitride compound semiconductor

[0012] Using the conventional single buffer layers of such like saidGaN, AIN, InN, SiNx, etc., makes the nitride film with an improvedcharacteristics in crystallographical view, but still has lots ofproblem to overcome the different physical characteristics betweensapphire and GaN.

[0013] Therefore, in order to get the nitride semiconductor layer withthe improved crystalline characteristics, new growth method ordevelopment of new buffer layer is necessary and this is the core forthe improved function of the final product, I.e. elements.

[0014] In order to solve the said problems, the present inventionprovides a method of manufacturing of nitride semiconductor layer withimproved electrical and crystalline characteristics by growth thenitride semiconductors on upper substrate of the nitride buffer layerwhich includes the aluminum.

[0015] The present invention provides a method of manufacturing ofnitride semiconductor layer comprising; the first step of growing abuffer layer including aluminum on the top of sapphire substrate; thesecond step of growing bivalent nitride buffer layers on the top of saidnitride buffer layers including aluminum; and the cathode ray tube futhe third step of growing a nitride semiconductor on the top of saidbivalent nitride buffer layers.

SUMMARY OF THE INVENTION

[0016] An object of the present invention is to provide A nitridesemiconductor comprising a metal oxide layer, said metal, formed on saidmetal oxide layer, a second nitride buffer layer formed on said firstnitride buffer layer, and a nitride layer formed on said nitride bufferlayers.

[0017] Another object of the present invention is to provide the nitridesemiconductor wherein said metal oxide layer is a sapphire substrate andsaid metal is aluminum.

[0018] Further object of the present invention is to provide the nitridesemiconductor, wherein said first and second nitride buffer layersinclude Indium.

[0019] According to an aspect of the present invention, the nitridesemiconductor, wherein said second nitride buffer layer is a bivalentnitride layer.

[0020] According to another aspect of the present invention, the nitridesemiconductor, wherein said third nitride buffer layer which does notinclude said metal, is formed between said first nitride buffer layerand said second nitride buffer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a cross-sectional view of nitride semiconductor layergrown as a conventional crystal growth method.

[0022]FIG. 2 is a cross-sectional view of nitride semiconductor layergrown as first embodiment of the present invention.

[0023]FIG. 3 is a cross-sectional view of nitride semiconductor layergrown as second embodiment of the present invention.

[0024]FIG. 4 is a cross-sectional view of nitride semiconductor layergrown as third embodiment of the present invention.

DETAILED DESCRIPTION

[0025] Basic idea of the present invention is to make a smoothconversion from sapphire substrate(Al2O3) to nitride semiconductor layerby growing the nitride buffer layer (AlxGayInzN, 0<x≦1, 0≦y≦1, 0≦z≦1)including aluminum, rather than the conventional single layer ofbivalent buffer(AlN, GaN, InN, SiNx), first on sapphire substrate, andthen growing a nitride semiconductor layer on the buffer layer. This canmake good crystalline characteristic of the nitride semiconductor layer.

[0026] Moreover, as shown the second embodiment below, the nitridebuffer layer(the GaxInyN and 0 x 1, 0 y 1) not including the aluminum(Al) and bivalent nitride buffer layer is grown additionally on nitridebuffer layer including aluminum, and the nitride semiconductor layer canbe grown thereon.

[0027]FIG. 2 is a cross-sectional view of a stacking structure of thenitride semiconductor layer grown by the crystal growth method followingthe first embodiment of the present invention. The nitride bufferlayer(21) is grown on the top of the sapphire substrate(20) and then,bivalent nitride buffer layer(22) is grown on the said nitride bufferlayer(21) including aluminum. After that, a nitride semiconductor isgrown on the top of said bivalent nitride buffer layer(22).

[0028] AlxGayInzN (0<x≦1, 0≦y≦1, 0≦z≦1) is preferred for the nitridebuffer layer including aluminum (21) and the layer of one selected fromAlN, GaN, InN and SiNx is preferred for bivalent nitride buffer layer.

[0029] And preferably, the last nitride semiconductor layer is GaNlayer.

[0030] Also, preferably, the nitride buffer layer(21) including aluminumand bivalent nitride buffer layer(22) are grown at the condition of400˜600° C. to have thickness of 10-1000 Å.

[0031] The effect for adding Indium(In) at the buffer layer is tocomplement the nitrides having high hardness relatively (because Inductile) and also to hinder generating dislocation and electric wave.

[0032] The reason of adding a buffer layer including aluminum on thesapphire substrate is as follows: the sapphire substrate has its surfacewherein in some part oxygen is replaced with Nitrogen throughnitrification. That is, by growing nitride buffer layer including thealuminum on the sapphire substrate, the progressive conversion from thesapphire substrate(Al2O3) to nitride layer can be induced.

[0033]FIG. 3 is a cross-sectional view of nitride semiconductor layer bythe crystal growth method following the second embodiment of the presentinvention, wherein the nitride buffer layer not including aluminum (31)is added between nitride buffer layer including aluminum (21) andbivalent nitride buffer layer (22) of the first embodiment of theinvention.

[0034] Preferably, nitride buffer layer not including aluminium (31) isGaxInyN layer (0≦x≦1, 0≦y≦1).

[0035] Preferably, the nitride buffer layer not including aluminium (31)is grown at the condition of 400˜600° C. to have thickness of 10-1000 Å.

[0036] The reason that the buffer layer of not including the aluminum isgrown on the buffer layer including the aluminum, and that GaN bufferlayer is grown on the said buffer layer not including aluminum, is formaking physical conversion to final GaN layer easy.

[0037] That is, GaN epi-layer is grown from sapphire substrate throughAlGaInN layer, GaInN layer and a GaN buffer layer, so that thisminimizes the difference of physical quality such as a coefficient ofthe thermal expansion and the lattice constant, between sapphiresubstrate and GaN layer.

[0038]FIG. 4 is a cross-sectional view of a stacking structure of thenitride semiconductor layer grown by crystal growth method following thethird embodiment of the present invention. The third embodiment iscomprised of adding additional nitride film (32) between nitride bufferlayer including aluminum (21) and sapphire substrate (20) of the firstor the second embodiment. The nitride film is formed sapphire substrate(20) by treating sapphire substrate (20) at the high temperature andletting ammonia(NH3) flow thereon.

[0039] It is examined by shooting x-rays at the nitride semiconductorgrown by the crystal growth method of the present invention, measuringan electrical and crystalline characteristics.

[0040] The GaN layer which is a nitride semiconductor layer grown bycrystal growth method of the present invention, has the improved FWHM ofapproximately 10%˜15% compared with single buffer layer such like AlN,GaN, InN and SiNx in respect of directions 002 and 102 of the wavelength which is measured in x-rays investigation.

[0041] In addition, a carrier mobility of GaN layer grown by the crystalgrowth method of the present invention is improved by 50% at maximum,and carrier density is decreased about (Mid)1016˜(High)1016 cm-3.

[0042] The nitride semiconductor layer grown by the crystal growthmethod of the present invention is improved in its electrical andcrystalline characteristics than those nitride semiconductor grown bythe conventional art.

Industrial Applicability

[0043] The present invention relates to a crystal growth method ofnitride semiconductor in which a nitride compound semiconductor aregrown at an upper portion of the nitride compound buffer layer includingaluminums so that it is possible to improve in characters forelectricity and crystallization.

[0044] The forgoing embodiments are merely exemplary and are not to beconstrued as limiting the present invention. The present teachings canbe readily applied to other types of nitrate buffer layers. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art.

1. A nitride semiconductor comprising a metal oxide layer, a firstnitride buffer layer which includes said metal, formed on said metaloxide layer, a second nitride buffer layer formed on said first nitridebuffer layer, and a nitride layer formed on said nitride buffer layers.2. The nitride semiconductor of claim 1, wherein said metal oxide layeris a sapphire substrate and said metal is aluminum.
 3. The nitridesemiconductor of claim 1, wherein said first and second nitride bufferlayers include Indium.
 4. The nitride semiconductor of claim 1, whereinsaid second nitride buffer layer is a bivalent nitride layer.
 5. Thenitride semiconductor of claim 1, wherein said third nitride bufferlayer which does not include said metal, is formed between said firstnitride buffer layer and said second nitride buffer
 6. The nitridesemiconductor of claim 1, wherein nitride film is formed between saidmetal oxide layer and first nitride buffer layer.
 7. A method ofmanufacturing a nitride semiconductor comprising; the first step offorming, on a metal oxide layer, a first nitride buffer layer includingsaid metal; a second step of forming a bivalent nitride buffer layers onsaid first nitride buffer layers; and a third step of forming a nitridesemiconductor on said second nitride buffer layer.
 8. The method ofmanufacturing a nitride semiconductor of claim 7, wherein said metaloxide layer is a sapphire substrate and said metal is aluminum.
 9. Themethod of manufacturing a nitride semiconductor of claim 7, wherein insaid first step, said first nitride buffer layer including said metal isformed on said metal oxide layer by the crystal growth method; in saidsecond step, said bivalent nitride buffer layers is formed on said firstnitride buffer layers by the crystal growth method; and in said thirdstep, said nitride semiconductor is formed on said second nitride bufferlayer by the crystal growth method.
 10. The method of manufacturing anitride semiconductor of claim 7, wherein said first nitride bufferlayer including metal and said second nitride buffer layer includeIndium.
 11. The method of manufacturing a nitride semiconductor of claim7, wherein said second nitride buffer layer is bivalent nitride layer.12. The method of manufacturing nitride semiconductor of claim 7,comprising, an additional step of forming third nitride buffer layerwhich does not include said metal, on the said first nitride bufferlayer, after said first step.
 13. The method of manufacturing nitridesemiconductor of claim 7, wherein said first nitride buffer layer is aAlxGayInzN (0<x≦1, 0≦y≦1, 0≦z≦1) layer.
 14. The method of manufacturingnitride semiconductor of claim 7, wherein said third nitride bufferlayer is the GaxInyN and (0≦x≦1, 0≦y≦1)
 15. The method of manufacturingnitride semiconductor of claim 7, wherein said second nitride bufferlayer is a layer of one selected from AIN, GaN, InN, and SiNx.
 16. Themethod of manufacturing nitride semiconductor of claim 15, wherein saidnitride semiconductor layer is a GaN layer.
 17. The method ofmanufacturing nitride semiconductor of claim 7, comprising additionalstep of forming a nitride film, after second step
 18. The method ofmanufacturing nitride semiconductor of claim 17, wherein said nitridefilm is formed on sapphire substrate by treating sapphire substrate atthe high temperature and letting ammonia(NH3) flow thereon.
 19. Themethod of manufacturing nitride semiconductor of claim 12, wherein saidfirst nitride buffer layer, said second nitride buffer layer and saidthird nitride buffer layer are grown at the condition of 400˜600° C. tohave thickness of 10-1000 Å.